Electrical propulsion unit for use in rarefied atmospheres



Feb. 21, 1967 H. GUTTON ETAL ELECTRICAL PROPULSION UNIT FOR USE INRAREFIED ATMOSPHERES 2 Sheets-Sheet 1 Filed June 24, 1964 24/rcuit-breaker Central Peat/Pier Pans/armer P- oscl /atar Source ofcums/16L T Feb. 21, 1967 H. GUTTON ETAL 3,304,717

ELECTRICAL PROPULSION UNIT FOR USE IN RAREFIED ATMOSPHERES Filed June24, 1964 2 Sheets-Sheet 2 United States Patent Office 3,304,717 PatentedFeb. 21, 1967 3,304,717 ELECTRICAL PROPULSION UNIT FOR USE IN RAREFIEDATMOSPHERES Henri Guttou, Neuilly-sur-Seine, and Maurice Pierre JosephFournet, Vincennes, France, assignors to Sud- Aviation Societe Nationalede Constructions Aeronautiques. Paris, France Filed June 24, 1964, Ser.No. 377.745 Claims prioritv, application France, July 2, 1963, 940,046,Patent 1,369,470 9 Claims. (Cl. 60-202) This invention relates to adevice for imparting orientated (hereinafter referred to as vectored)impulses to an object moving through a rarefied atmosphere, and is moreparticularly though not exclusively applicable for correcting thevelocity or attitude of a space vehicle such as an artificial satellite.

By reason of the very small gravitational force acting on such movingobjects, a very small force will suflice to move a relatively large massunder such conditions.

Chemical rockets have been used to this end but entail the need to carrya large quantity of fuel, thus making them unduly heavy.

Recourse has also been had to electric propulsion units in which thethrust is obtained by ejecting a small mass of elementary particlespossessed of very high velocity.

Among the latter-mentioned types of propulsion units may be mentionedarc or resistance type electrothermal engines, ion engines,magnetohydrodynamic engines, and plasma engines with heated wireelectrodes. All these propulsion units must be equipped either withmeans for generating the heat required for particle emission, or with adual electric power supply system, and in either case it is mandatory toprovide a source capable of supplying the power required, and such asource is liable to be too heavy.

All the foregoing systems referred to have the disadvantage of theirlarge weight or their complexity, or else of the short life of theirparticle emitter as the result of heat losses due to vaporization, thusnecessitating replacement of the emitter for space flights of longduration. Moreover, in certain cases, the positive or negative charge ofthe particles emitted and their attraction by the vehicle itselfimmediately subsequent to ejection implies the use of a particleneutralization system.

It is the object of the present invention to provide a simple,lightweight electric propulsion unit operating under cold conditions,from which all the particles emitted are neutral, which has satisfactoryenergy efficiency and which can therefore be used with advantage onspace vehicles.

The invention is based on the following successive observations made bythe applicants:

If one takes a straight conductive element initially assumed to beexposed to the surrounding air and if one causes direct current ofincreasing intensity to flow through this conductor, then thetemperature of the latter will gradually rise until the current is cutoff by a local melting process.

If instead of flowing direct current through the con ductor the latteris subjected to current pulses of short duration with steep leadingedges, for instance by causing the current discharged by a capacitor toflow through the conductor, while at the same time gradually increasingthe amplitude of the current, then the temperature of the conductor atthe end of the pulse gradually increases until a break takes placethrough melting.

Repeating the same experiments in a rarefied atmosphere with an ambientpressure below 133.10 pascals, 10* Torr, or 136.10* leg/c11 say if theconductor is caused to be the seat of direct current or low-frequencycurrent, it will begin to redden and will then initiate an evaporationprocess which is progressively accelerated until the circuit is broken.

When the conductor is subjected to brief pulses with steep leading edgesunder such rarefied environmental conditions, the phenomenon iscompletely transformed. The conductor apparently remains cold and, abovea certain threshold, a brief flash occurs around the conductor. Sensorspositioned remote from the conductor indicate the flight of neutral orelectrified particles through the surrounding space at very highvelocities of the order of several tens of kilometres per second.Indeed, everything suggests that the flow of the current with the steepleading edge no longer takes place through the entire body of theconductor but is confined toan extremely thin surface layer thereofwhich is destroyed by the current, after which the latter no longerflows through the conductor itself but through the plasma surroundingit.

Most of the electrical energy supplied to the conductor, instead ofappearing in the form of heat within the conductor itself, is convertedinto kinetic energy imparted to elementary particles.

It is noteworthy that the total mass ejected at each impulse isextremely low, that this ejected mass appears only in the form ofelementary particles and, lastly, that the velocities imparted to theparticles are very considerable. It was also observed that a givenconductor could withstand a considerable number of impulses.

With a view to utilizing this property in devices designed to impart toa moving object, in a rarefied atmospherc, vectored impulses formodifying its velocity and/or its attitude, the present inventionprovides an electric propulsion unit characterized in that it comprisesa conductor inserted into a circuit which supp-lies current pulses ofshort duration but steep leading edge, which conductor is associated tomeans for vectoring the elementary particles possessed of very highvelocity which are generated by said conductor, the latter remainingapparently cold, and in the plasma surrounding it, the complete unitbeing disposed within an ambient atmosphere in which the prevailingpressure is below a few thousandths of a Torr or tenths of a gram persquare centimetre. As a result, the elementary particles ejected in thedirection predetermined by said vectoring means produce a likewisevectored propelling reaction force which is transmitted to the vehicleequipped with such a propulsion unit.

In one preferred form of embodiment, said vectoring means acts upon theconduct-or having a polydirectional emission environment in such mannerthat the joint action of the various ejected particles after reflectionupon a mirror, for example, produce a vectored resultant impulse.

In an alternative form of embodiment, the vectoring system is astructural part of the conductor itself whereby the current is caused toflow preferentially over one of the conductor faces to the detriment ofthe others thereby furnishing an emission which is selectively directed.

This invention consequently contemplates industrial applications of suchan electrical generator which may be, for example, correction of thevelocity or attitude of a space vehicle such as an artificial satellite,or correction of the motion of a rotary engine by mounting such agenerator at an extremity of a lever arm, said generator being used as asingle unit forming one element of a group of generators.

The description which follows with reference to the accompanyingnon-limitative exemplary drawings will give a clear understanding of howthe invention can be carried into practice and will disclose yet furtherfeatures thereof.

In the drawings:

FIG. 1 is a block diagram of an electric power supply for a propulsionunit according to the invention;

FIG. 2 schematically illustrates a first constructional form of apropulsion unit according to the invention;

FIGS. 3 and 4 are respectively a plan view with partial cut-away and asectional view through the line IV-IV of FIG. 3 of a possible form ofembodiment of a propulsion unit of the kind schematically illustrated inFIG. 2;

FIG. 5 is a schematic sectional view of the propulsive force generatingelement in an alternative form of embodiment of a propulsion unitaccording to the invention;

FIG. 6 is a perspective view with partial cut-away of a form ofembodiment of the propulsion unit schematically illustrated in FIG. 5

FIG. 7 is a schematic sectional view of an alternative constructionalform of the propulsive force generating element of FIG. 5;

FIG. 8 is a block diagram of another electric power supply for apropulsion unit according to the invention;

FIG. 9 is a sectional view similar to that of FIG. 4 for another form ofembodiment of a propulsion unit of the kind schematically illustrated inFIG. 2;

FIG. 10 is a schematic sectional view of another alternativeconstructional form of the propulsive force generating element of FIG.5;

FIG. 11 is a block diagram of the electric power supply for a group ofpropulsion units which act simultaneously; and

FIG. 12 is a block diagram of the electric power supply for a group ofpropulsion units which do not act simultaneously.

Referring first to FIG. 1, it will be seen that a source of low-voltagecurrent 1 such as a solar battery is utilized to feed a self-oscillator2 which transforms this direct current into alternating current. Atransformer 3 steps up the voltage of this current which then passesthrough the rectifier 4. The system 1, 2, 3, 4 behaves in the manner ofa high voltage D.C. source supplying current at several thousand volts.This source is used to charge a capacitor 5 of several microfaradsthrough impedance coil 6. Reference numeral 7 designates a switch whichmay be either a mechanical switch, an electronic switch, an ion switch,or lastly either a natural electric arc or an electric are driven forinstance by the pilot spark generating unit 24. The propulsive conductorto be energized is denoted by reference numeral 8. The capacitor may becharged directly by a source of high voltage direct current such as thesource 1a of FIG. 8.

FIGS. 2 through 4 show a propulsion unit in which the conductorenvironment is operated upon whereby to cause the action of the variousejected particles to jointly produce a vectored or directed resultantimpulse.

In this first form of embodiment of the propulsive con ductor, recourseis had to a linear conductor as desig nated in sectional form by thereference numeral 9 in FIG. 2, and this conductor is surrounded by amirror 10, whereby only the particles ejected in the direction E giverise to a propulsive reaction force.

In this first constructional form of such a propulsion unit, shown inFIGS. 3 and 4, the propulsive conductor proper is a graphite rod 11. Thecurrent lead-in conductors 12 and 13 are two metal strips separated byan intermediate strip of insulating material 14 made, for instance, oflaminated fiberglass. The two strips 12 and 13 are very closely spacedfrom each other in order to minimize the inductance of the circuit andfacilitate the establishment of the current peak.

The mirror 15 is of cuplike shape, being made of glass or ceramic forinstance, and being of substantially parallelopiped form with one face Fmissing.

Preferably, the conductive strips 12 and 13 are extended either by twobent parallel portions 12a and 13a as shown in FIG. 3, or by twoparallel conductive strips respectively connected to the ends of thepropulsive con- 4 ductor 11, whereby to director vector the ejection ofthe plasma which appears after ejection of the particles.

By reason of the small weight of its component parts, the propulsionunit of FIGS. 3 and 4 can be secured directly through the medium of theconductive strips 12 and 13, in view of the small thrusts generated bythe unit and the low inertia loads set up during the acceleration periodand due to the low weight of said propulsion unit. The latter mayalternatively be used without the glass or ceramic cup 15, theinsulating strip 14b then serving as a reflector as illustrated in FIG.9 wherein the elements similar to those. of FIG. 4 have the samereference numerals followed by the letter b. Alternatively, also, thepropulsion unit could be secured to the space vehicle through theinsulating cup.

Reference is next had to FIGS. 5 through 7 for an illustration of asecond type of propulsion unit according to the invention, in which thestructure of the conductor itself is operated on in order to obtainpreferential flow of the current over one of the conductor faces to thedetriment of the others.

FIG. 5 schematically illustrates the propulsion force generating elementof such a propulsion unit of the second type referred to. This elementis a two-part element, of which one part 16 is made of a material suchthat a current with a steep leading edge remains concentrated on itsouter surface with only very shallow penetration into its body, whilethe other part 17 is made of a material into which a current with asteep leading edge can penetrate more deeply.

A conductor of this type can be obtained, for instance,

by juxtaposing and bonding together two rods made of materials havingdifferent electrical conductivities, that of the part 17 being 50 totimes lower than that of the part 16. As an example said rods are madeof two sintered materials of different graphites, the more highlyconductive rod being located at 16, i.e. on the same side as theemission E. The binding agent may be made conductive either bypolymerization or by treating it with a conductive dopant.Alternatively, such a propulsion unit of the second type can be obtainedby directly pressing two suitable powder preparations, i.e. havingdifferent conductivities within the aforementioned range, and thesepreparations are then solidified and rigidly united by polymerization,as in the fabrication of resistors utilized in the radio and electricalengineering art. In a resistor of this type, when an impulse occurs, thelines of current concentrate in the region of the surface e of theelement 16 and the particles are ejected only through this face e andabout a line at right angles thereto.

In the specific constructional form of a propulsion unit of the secondtype shown in FIG. 6, the two conductor elements 16a and 17a, theproperties of which are similar to those of the elements 16 and 17 ofFIG. 5, are embedded into supports 18 mounted on conductor strips 19 and20 which are bent into Z-shape and themselves embedded into aninsulating block 21 serving to secure the propulsion unit. TheseZ-shaped strips 19 and 20 are reversed between each other with theirwings parallel. Their more distant wings which are connected to theconductor elements 16a and 17a can be extended in mutual parallelism, asat 1911 and 20a in FIG. 6, whereby to expel the plasma which appearsafter the particles have been ejected.

In order to cause the current lines to concentrate in the region of theface e of the propulsion element of FIG. 5, the three other faces ofsaid element have disposed thereon a U-shaped channel section made ofmagnetic material. Alternatively, such concentration can be obtained inthe manner shown in FIG. 7, the conductor 22 being then obtained byconcretion into a U-shaped channel-section 23 in magnetic material, orby charging the zone 23a with magnetic powder over all sides of theconductor 22a other than its emitting face e. (FIG. 10).

It goes without saying that the current pulses may be repeated severaltimes, whereby the cumulative successive impulses resulting therefromproduce a true propulsion effect. Indeed, such an experiment has beenconducted by the applicants with complete success.

In its various applications, the subject electric propulsion unit ofthis invention may comprise, not one, but a plurality of propulsiveelements of the type hereinbefore described, in order to increase thethrust otherwise than by merely increasing the size of each unit elementor in order to obtain different effects at different times.

Thus, for increasing the thrust, a plurality of propulsive conductors8a, 8b, by a common rectifier 4b, each one of said propulsive elementsbeing associated with its capacitor 5a, 5b, its impedance coil 6a, 6b,and its switch 7a, 7b, controlled by the respective circu-it-breakercontrolling unit 24a, 24b, as illustrated in FIG. 11.

In case it is desired to obtain different propulsive effects atdifferent times,. the propulsion unit, as illustrated in FIG. 11,comprises a plurality of propulsion conductors 8c, 8d, 8e, which areenergized by a common capacitor 50 through a selecting switch 25remotely controlled by any known means.

Each one of conductors 8a, 8b, 8c, 8d, 8e the type illustrated in FIGS.4 to 7, 9 and 10.

A propulsion unit according to this invention may be utilized in orderto exert a direct thrust on an object moving through a rarefiedatmosphere or through space. It may likewise be mounted on the end of alever arm and act as a rotary engine usable for driving equipment in avacuum.

The fact that the conductor apparently remains cold in operationindicates that the energy efficiency of the system is high. Indeed, theenergy supply can be made virtually limitless by the use of solarbatteries. In addition, in its specific application to space vehicles,the system permits flexible, inertia-free transmission of the commandsreceived from the ground, from a programmed system, or from a pilot.

It will of course be understood that many modifications or substitutionsof parts may be made to the specific embodiments as hereinbeforedescribed without departing from the scope of the present invention asspecified in the appended claims.

What We claim is:

1. An electric propulsion unit for use in rarefied atmospherescomprising, in combination, means for generating current pulses of shortduration with a steep leading edge and, within an ambient atmosphere inwhich the prevailing pressure is below a few tenths of a gram per squarecentimetre, a conductor made of a graphite rod, two very closely spacedmetal strips substantially parallel to said rod and respectivelyconnected to the ends thereof, a strip of insulating material disposedbetween said metal strips, means for connecting said metal strips tosaid pulse generating means, whereby when said rod is fed by said pulsegenerating means it ejects elementary particles at very high velocities,while remaining cold and is surrounded by a plasma, and a mirror ofreflecting material surrounding said rod and the parts of said metalstrips connected thereto.

2. A propulsion unit according to claim 1, wherein said metal strips areetxended in mutual parallelism beyond the ends of said rod in adirection perpendicular to the latter toward the open end of the mirror.

3. A propulsion unit according to claim 1, wherein the mirror consistsof a cup having a parallelopiped shape with an open face located on thesame side of the metal strips as the graphite rod.

4. A propulsion unit according to claim 1, wherein the mirror consistsof the strip of insulating material.

5. An electric propulsion unit for use in rarefied atmospherescomprising, in combination, means for generating is of aresimultaneously energized current pulses of short duration with a steepleading edge and, within an ambient atmosphere in which the prevailingpressure is below a few tenths of a gram per square centimetre, aconductor consisting of a rectangular rod, means for connecting saidconductor to said current pulse generating means, whereby when saidconductor is energized by said pulse generating means it ejectselementary particles at very high velocities, while remaining cold andis surrounded by a plasma, and a U-shaped channel-section of magneticmaterial surrounding three faces of said rectangular rod the fourth faceof which acts as an emission face for the elementary particles and theplasma.

6. An electric propulsion unit for use in rarefied atmospherescomprising, in combination, means for generating current pulses of shortduration with a steep leading edge and, within an ambient atmosphere inwhich the prevailing pressure is below a few tenths of a gram per squarecentimetre, a conductor consisting of a rectangular rod, means forconnecting said conductor to said current pulse generating means,whereby when said conductor is energized by said pulse generating meansit ejects elementary particles at very high velocities, while remainingcold and is surrounded by a plasma, and a magnetic powder covering threefaces of said rectangular rod the fourth face of which acts as anemission face for the elementary particles and the plasma.

7. An electric propulsion unit for use in rarefied atmospherescomprising, in combination, means for generating electric current pulsesof short duration with a steep leading edge, a thick solid electricalconductor situated within an ambient atmosphere the pressure of which isless than a few tenths of a gram per square centimeter, means forelectrically connecting said conductor to said electrical current pulsegenerating means, whereby when said conductor is energized by saidgenerating means, under the action of each electrical current pulsehaving a steep leading edge, there is ejected from said conductor insubstantially cold condition and without apparent deterioration, a smallquantity of its constitutive material in the form of elementaryparticles, said elementary particles immediately generating a plasmaunder the influence of the electric voltage prevailing in saidconductor, said plasma surrounding said conductor, and means foraccelerating and directing said ejected particles and generated plasma.

8. An electric propulsion unit as claimed in claim 7, wherein said thicksolid electrical conductor is constituted of two juxtaposed elementaryconductors having different resistivities, said elementary conductorsbeing juxtaposed whereby a preferential electric current flow isobtained in the elementary conductor having the lesser resistivity andconsequent ejection of elementary particles is produced from the freesurface of said conductors having the lesser resistivity in greaterquantity relative to the ejection of particles produced at the contactface between said elementary conductors.

9. An electric propulsion unit for use in rarefied atmospherescomprising, in combination, means for generating electric current pulsesof short duration with a steep leading edge, a thick solid electricalconductor situated within an ambient atmosphere the pressure of which isless than a few tenths of a gram per square centimeter, an electricalconductor constituted of two thick solid rods of electrically conductivematerials the electrical conductivities of which differ from each otherfrom about fifty fold to about a hundred fold, said rods beingjuxtaposed with interposition of a binding agent, the rod having thehigher conductivity being disposed on the side of desired ejection ofelementary particles under the action of said pulses, two electricallyconducting strips electrically connected to said rods, with said rodsdisposed between said strips, said strip having parallel first wings onsaid side of desired ejection of said elementary particles and of aplasma they generate under the action of electric voltage in said rods,said 7 8 strips having second wings closer to each other on a sec-References Cited by the Examiner 0nd side opposite said side of desiredejection, insulating UNITED STATES PATENTS material between said secondwings and electrical connecting means between said second wings and saidgenerating 2,764,707 9/1956 Crawford et 313-63 means, whereby when saidconductor is energized by said 5 2,940,011 6/1960 Kolb' generatingmeans, ejection of elementary particles is pfo- 237x332 3/1961 duced onsaid side of desired ejection and, by ionization of 3204389 9/1965Schwmghamer 60-355 X said particles, between said wings, there is formeda plasma which is propelled in the direction of the extremities ofCARLTON CROYLE Pnmary Exammer' said first wings. 10 MARK M. NEWMAN,Examiner.

1. AN ELECTRIC PROPULSION UNIT FOR USE IN RAREFIED ATMOSPHERESCOMPRISING, IN COMBINATION, MEANS FOR GENERATING CURRENT PULSES OF SHORTDURATION WITH A STEEP LEADING EDGE AND, WITHIN AN AMBIENT ATMOSPHERE INWHICH THE PREVAILING PRESSURE IS BELOW A FEW TENTHS OF A GRAM PER SQUARECENTIMETRE, A CONDUCTOR MADE OF A GRAPHITE ROD, TWO VERY CLOSELY SPACEDMETAL STRIPS SUBSTANTIALLY PARALLEL TO SAID ROD AND RESPECTIVELYCONNECTED TO THE ENDS THEREOF, A STRIP OF INSULATING MATERIAL DISPOSEDBETWEEN SAID METAL STRIPS, MEANS FOR CONNECTING SAID METAL STRIPS TOSAID PULSE GEN ERATING MEANS, WHEREBY WHEN SAID ROD IS FED BY SAID PULSEGENERATING MEANS IT EJECTS ELEMENTARY PARTICLES AT VERY HIGH VELOCITIES,WHILE REMAINING COLD AND IS SURROUNDED BY A PLASMA, AND A MIRROR OFREFLECTING MATERIAL SURROUNDING SAID ROD AND THE PARTS OF SAID METALSTRIPS CONNECTED THERETO.